1. Future Climate Change in the Pacific Northwest
Cliff Mass, Atmospheric Sciences
University of Washington

2. There has been a great deal of contradictory information about global warming and its influence on the Northwest

3. Some environment groups have proposed that global warming has already caused our precipitation to become more extreme

4. And local media have aired stories saying storms are getting more intense

5. In contrast, others hold that there is no strong evidence for current or future changes
ill

6. Some suggest that the recent “pause” means global warming is not occurring

7. …while thousands of scientists from around the world have written a series of reports indicating the imminent threat of global warming due to mankind’s influence

8. Intergovernmental Panel on Climate Change (IPCC) Reports

9. What can climate prediction technology tell us
What can climate prediction technology tell us? What do we know for sure? What are the uncertainties? What will happen here?

10. Human-forced (anthropogenic) climate change has already hit our region
Even without any effects from increasing greenhouse gases like CO2

11. Massive Irrigation in Eastern WA

12. The result: cooling of 1-4 °F and higher humidity

13. Plowed fields: Eastern WA dust storms

14. Seattle’s urban core is often 2-10F warmer than it would have been without concrete and buildings

15. Bottom Line
Humans have already changed the climate

16. Increasing Greenhouse Gases

17. Greenhouse gases warm the planet
Carbon Dioxide
Water Vapor
Methane
Nitrous Oxide
… and others
Greenhouse Gas Emissions

18. Greenhouse gases act like a blanket Thicker blankets (or more of them) make you warmer

19. CO2 oncentrations are increasing rapidly

20. We predict the impacts of increasing greenhouse gases using global climate models (GCMs)
Sophisticated computer simulations based on the physics of the atmosphere and ocean.
Atmospheric parts are nearly identical to weather prediction models, which are tested every day, but with atmospheric gases vary in time.

21. Climate Prediction Technology
We run coupled global atmosphere-ocean models for decades or centuries.
Use the most powerful supercomputers.
Have to make assumptions about greenhouse gas emissions. How will they change in time?
There about two-dozen international groups doing such simulations.

22. Climate Model Output for 210022

23. Global Warming is NOT Uniform
Arctic warms quickly for a number of reasons, including the melting of sea ice.
Continents warm up more than oceans.
Eastern oceans up less than western oceans.
In general, the dry areas (e.g., the SW U.S.) get drier and wet areas (e.g., British Columbia) get wetter.

24. Temperature Northwest warming delayed and slowed by the Pacific Ocean
Observed Winter Surface Temperature Change ( )

25. Without Pacific warming, our mountain snowpack has not changed much over 30 yr

26. Global climate models are too coarse to simulate the effects of critical Northwest terrain
Climate Model Terrain

27. A new technology to solve the resolution issue: Regional Climate Modeling

28. Change in Winter Surface Air Temperatures (F)28

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32. What about water, our most precious resource?

33. Good news for average precipitation
Unlike some areas, we will still have plenty of precipitation, just more rain and less snow

34. NCAR Global Model (Winter Precipitation Trend, 2005-2060)

35. Change in Snowpack from 1990 to 2090
But warming will result in more precipitation falling as rain rather than snow
Change in Snowpack from 1990 to 2090
-40% 0%
+40%

36. But there is a dark side to the our future warmth: more extreme precipitation and flooding

37. Super Atmospheric Rivers

38. When atmospheric rivers hit our terrain, intense precipitation falls

39. Global warming will intensify atmospheric rivers
Warmer air holds more water vapor.
Examined a large collection of climate models simulation for changes from to based on “business as usual” greenhouse gas emissions.
Precipitation on extreme atmospheric river days increases by 15-39% .

40. Flooding Potential Increases
Snow absorbs rain.
With less snow, there will be less “protection.”
Thus, heavier rainfall could lead to greater flooding on major rivers.

41. Northwest Windstorms Will there be more of them?
Will they become more intense?
The Inauguration Day Storm
1993

42. Northwest Windstorms The answer appears to be no. No increasing trend.
UW investigated this issue for Seattle City Light

43. Can we predict climate decades ahead when we can’t forecast next week’s weather?

45. In weather prediction we forecast the exact state of the atmosphere at some time in the future
Tomorrow’s high in Spokane will be 67F
It will rain tomorrow afternoon after 3 PM

46. In Climate Prediction We DON’T Do This
We predict average quantities over extended periods.
Example: the mean winter temperatures will be 3F higher over the Pacific Northwest.
The average conditions are closely controlled by the amount of radiation reaching and leaving the planet
We have a good handle in changes in radiation, IF WE KNOW THE ATMOSPHERIC COMPOSITION.

47. Major Take Home Messages
Global warming from greenhouse gases has had only a small influence on our region so far. Natural variability has dominated over human forcing.
That will change, particularly by the end of the century. Less warming near the coast, more in eastern Washington. Think 3-8F during the winter.
Annual precipitation will remain the same or increase slightly

48. Take Home
Significant (30-70%) drops in mountain snowpack by the end of the century
Atmospheric rivers will be stronger, with heavier rainfall and more flooding.
No increase in windstorms
Beware those that hype current weather events as indications of global warming.
Those who claim that GW is not an issue are equally wrong.

49. The End